“Millo” means a rampart, mound

Millo: a place in ancient Jerusalem. Both name and place seem to have been already in existence when the city was taken from the Jebusites by David. (2 Samuel 5:9; 1 Chronicles 11:8) Its repair or restoration was one of the great works for which Solomon raised his "levy," (1 Kings 9:15,24; 11:27) and it formed a prominent part of the fortifications by which Hezekiah prepared for the approach of the Assyrians. (2 Chronicles 32:5) The last passage seems to show that "the Milo" was part of the "city of David," that is, of Zion. Comp. (2 Kings 12:20)